The menopause and its associated insomnia makes women age faster, according to new study.
Scientists calculated that a woman who entered the menopause at 42 would, by the age of 50, be a full year older biologically than a woman who became menopausal at 50.
And postmenopausal women with insomnia appeared to be an average of two years old biologically than those who did not have trouble sleeping, although the researchers cautioned they could not “conclude definitively” that this was the result of insomnia.
The biological age was calculated using an ‘epigenetic clock’, which measures changes to the way genes are expressed, some of which are associated with ageing.
One of the researchers, Professor Steve Horvath, a geneticist at University of California, Los Angeles, said: “For decades, scientists have disagreed over whether menopause causes ageing or ageing causes menopause.
“It's like the chicken or the egg: which came first? Our study is the first to demonstrate that menopause makes you age faster.
“We discovered that menopause speeds up cellular aging by an average of six per cent. That doesn't sound like much but it adds up over a woman's lifespan.”
As part of the study, the scientists tracked methylation, a chemical biomarker linked to ageing, to analyse DNA samples from more than 3,100 women.
In separate research about the effects of sleep problems on ageing, Professor Judith Carroll, also of UCLA, and colleagues looked at data about more than 2,000 women using the epigenetic clock,
They found that postmenopausal women with five symptoms of insomnia were an average of two years old biologically than those who had no symptoms.
Professor Carroll added: “We can't conclude definitively from our study that the insomnia leads to the increased epigenetic age, but these are powerful findings.
“In the future, we will need to carry out studies of the same individuals over an extended period of time to determine cause-and-effect relationships between biological age and sleep disorders.”
Professor Horvath said the research could lead to new drugs to minimise the effect of the menopause.
"The big question is which menopausal hormone therapy offers the strongest anti-aging effect while limiting health risks," he said.
"No longer will researchers need to follow patients for years to track their health and occurrence of diseases. Instead we can use the epigenetic clock to monitor their cells' ageing rate and to evaluate which therapies slow the biological aging process.
"This could greatly reduce the length and costs of clinical trials and speed benefits to women."
The studies were published in two journals, the Proceedings of the National Academy of Sciences and Biological Psychiatry.